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M-JPEG



General Information
Overview
There are three JPEG-based codecs built into QuickTime. These are: Photo-JPEG, MJPEG-A and MJPEG-B. MJPEG stands for "Motion JPEG," and is identical to Photo-JPEG except that the MJPEG codecs have translators built-in to support the different capture cards.

MJPEG is not the same as MPEG, although the names are confusingly similar. The primary difference is that MPEG provides temporal compression, while MJPEG only provides spatial compression.
Architectures Supported
Pros, Cons & Tips
Pros
  • MJPEG codecs are often used as storage formats for large files that need to be archived with good quality. It is a lossy codec, but at 100% quality, the image degradation is minimal.
  • At WWW data rates (5-20K), JPEG may produce better results than Cinepak.

Cons
  • All the JPEG codecs require significant amounts of CPU power and are not well suited to video playback at CD-ROM or higher data rates, except when assisted by a hardware capture card.
  • Large image and/or high frame rate movies usually don't play smoothly.

Tips
  • Avoid saving the same file multiple times with any JPEG codec, as the JPEG artifacts may build up and become objectionable.


Ideal source material Video
Supported bit depths 24-bit color, 8-bit greyscale
Compression time Asymmetrical
Temporal compression? No
Special features Supports Media Cleaner Pro 2.0's advanced data rate limiting
Encoder requirements Any MacOS or Windows
Decoder requirements Any MacOS or Windows
Encoder availability Built into QuickTime 2.5
Decoder availability Built into QuickTime 2.5
Algorithm Discrete Cosine Transform (DCT)
Manufacturer Apple


If you have any comments or tips & tricks to share about MJPEG, please contact us at info@terran-int.com.



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